The country's five richest families are wealthier than the poorest 20% of the population, a leading charity has revealed.

A report by Oxfam showed that, at £28.2 billion, the combined wealth of the top five billionaires and their families is more than the £28.1 billion of the 12.6 million people who are society's poorest.

Titled A Tale Of Two Britains, the report shows that 0.1% of the population have seen their income grow by £24,000 a year, while the incomes of the poorest 90% of Britons have gone up by an average of £2.82 a week, or £147 a year.

Britain's richest family, the Grosvenors, headed by the Duke of Westminster, has a fortune of around £7.9 billion, which is more than the bottom 10% of the population combined. The Grosvenors' wealth derives largely from owning 190 acres of real estate in London's Belgravia, near Buckingham Palace, according to the Forbes rich list.

Widening inequality creates a "vicious circle where wealth and power are increasingly concentrated in the hands of a few, leaving the rest behind," says the report.

"The extreme levels of wealth inequality occurring in Britain today threaten to exclude the poorest, whose standards of living are being squeezed as they are hit by increasing costs for basics like food and energy bills and cuts to services and support when they are most needed," it says.

The top five richest families also include David and Simon Reuben, whose £6.9 billion fortune comes from metals and property, and the Hinduja brothers, whose trucking and banking businesses have netted them £6 billion.

The Cadogan family is worth around £4 billion from owning property and land in Chelsea and Knightsbridge in London and Cadogan Estates, while the fifth richest person is Newcastle United FC owner and Sports Direct clothing chain boss Mike Ashley, whose fortune is valued at £3.3 billion.

Oxfam also warned of the UK's growing "tax gap", estimating that at least £5.2 billion a year is evaded by wealthy individuals using tax havens, the equivalent of £200 a year for every household in the UK.

The charity urged the Government to balance its books by "clamping down on companies and individuals who avoid paying their fair share of tax and starting to explore greater taxation of extreme wealth".

Ben Phillips, Oxfam's director of campaigns and policy, said: "Britain is becoming a deeply divided nation, with a wealthy elite who are seeing their incomes spiral up, whilst millions of families are struggling to make ends meet.

"It's deeply worrying that these extreme levels of wealth inequality exist in Britain today, where just a handful of people have more money than millions struggling to survive on the breadline."

He added: "Increasing inequality is a sign of economic failure rather than success. It's far from inevitable - a result of political choices that can be reversed. It's time for our leaders to stand up and be counted on this issue."

The research was compiled using billionaire data from the Forbes rich list and Credit Suisse's Global Wealth Databook to calculate the wealth of the bottom 10% and 20% of the population.

In January, an Oxfam report found that the richest 85 billionaires on the planet own the same amount between them as half the world's population, or 3.5 billion people.